Rivet cutting gun



0d. 27, 1931. E. w. STEVENS RIVET CUTTING GUN Filed June 19, 1928 2 Sheets-Sheet l fdrmrd/l/ Jferens /m A TTORNE Y.

N) INVENTOR.

Patented Oct. 27, 1931 v UNITED STATES PATENT OFFICE EDWARD W. STEVENS, F DETROIT, MICHIGAN, ASSIGNOR T0 CHICAGO IPNEUMATIG TOOL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY mvn'r currnm GUN Application filed June 19,

This invention relates to vfluid pressure tools and more specifically to large pneumatic hammers used in demolition work, as in cutting off bolt and rivet heads and punching out rivets, such toolsbeing commonly referred to as rivet cutting guns. On account of their size and weight such tools frequently require at least two men to operate,

' one to direct the demolishing end of the gun and the other to control the motive fluid. A tool of'this type strikes a single blow in one position of the throttle handle which is then moved to a different position to effect the return or non-working stroke of the piston.

Oneobject of the invention is to provide an improved form of control valve for the motive fluid. Another object .is to secure a full and forceful blow by providing for the time element involved in the manual throw of the valve to the forward position thereby to insure a full head of motive fluid upon the piston at the beginning of its forward stroke. Another object is to insure proper lubrication of the control valve and a lasting seal 1 views similar to Fig. 3 showing the valve in different operative positions.

The embodiment of the invention chosen for the purpose of illustration comprises a fluid pressure hammer adapted for demolition work and comprising a long cylinder S providing a piston chamber within which reciprocates a free piston which delivers its blow directly upon the shank of a working tool such as a rivet cutting chisei 8 which is supported in a guide bushing 9 threaded into a front head 10 secured tocylinder 6 and having a handle 3.1 for supporting the forward 1828. Serial N0. 286,621. 7

end of the tool and directing it to the work. A heavy coil spring 12 may be interposed between guide bushing 9 and the forward end of cylinder 6 to absorb the blow of piston 7 I and prevent breakage of the front head in the event that the working tool 8 is not in proper position. The cylinder may provide a free atmospheric vent or exhaust port 6a controlled by piston 7. I

The rearward end of cylinder (5 has secured thereto in any suitable or desired manner a the back head 13 terminates in a boss 13?; having a central threaded opening 130 for a fluid pressure conduit. Boss 13?) also has a bore therethrough in which is rigidly socured a handle 16 for supporting the tool.

' A cylindrical valve 17, of a size and taper to fit the bore 13a in the back head, is disposed therein to control the pressure fluid for operating piston 7 Valve 17 has a reduced portion 1 as head at one side and to have keyed thereto a handle 18 by which valve 17 is manually rotated or oscillated. Stops 19 and 20 (Fig. l), are provided on the back head in position to be engaged by handle 18 and to limit its movement. Securing means, such as a nut 21, may be provided to hold handle 18 in place. The large end of valve 17 has a reduced axial extension 17?) which projects through the bore 14a of closure 14 and therebeyond, the extension being threaded to receive a castle nut 22. Surrounding eatension 17?) and interposed between valve 1'? and closure 14 are resilient means which may take the form of a coil s )rm 23 which 'HQlLiUW'lV h a) i) i.

urges valve 17 into close contact with the tapered bore of valve chamber and the means on valve 1? for contracting the we arranged to extend beyond the back ill) I same are disposed substantially centrallyof the valve.

In order properly to lubricate valve 17 and to prevent leakage of the pressure fluid from the central portion of the valve chamber,

suitable means are provided adjacent the valve are shown in Figs. 3, 4, and 5 which also indicate, in dotted outline, corresponding positions of the valve handle. As indicated. valve 17 has in its central portion a large arcuate groove or recess .24, a portion of which always registers with the passage leading to the rear end of the piston chamber, connecting the same either with the fluid inlet A or with an atmospheric exhaust port 26. The valve also has a small groove or'recess 527 which may register with fluid inlet A alone, as in Fig. 3, or passpressure fluid in restricted amount to a passage 28 (Fig. 4) connecting by a flexible-conduit 28a to the forward end of the piston chamber to drive the piston on its return stroke, or connect passage 28 to an atmospheric exhaust 29 (Fig. 5). \Vith the valve in the position shown in Fig. 3 (handle 18 being against stop 19) the, piston is at rest and the fluid inlet A is closed off. On advancing handle 18 to a mid-position between stops 19 and 20, the rear end of the piston chamber continues to be connected to the exhaust by valve recess 24' and pressure fluidin limited amount is passed to the forward end of the piston chamber by rrcess 27, passage 28, and conduit 28a. As shown and by preference port 2511 of passage 25 is spaced somewhat from the rearward end of the piston chamber so as to be sealed or closed momentarily by piston 7 at the end of its rearward stroke, the piston then ex tcnding into a pocket from which it rebounds by the action of the air which it traps and compresses therein. This action of the iston provides an. interval of time during which the operator moves valve control handle 18 to the forward position against stop Fig.5) so that when the piston uncovers port 250, pressure fluid at full volume enters the piston chamber insuring a blow of full power. This is an important advantage over the usual practice of stopping the piston on its rearward stroke by directing the pressure fluid released by the manual control valve/directly into the real-most portion of the piston chamber. The former practice stops the piston suddenly and reverses its movement with the result that the piston is carried on its forward stroke a considerable distance before a full opening of the throttle is accomplished with the result that the piston does. not reach its maximum velocity when it arrives at the striking point. Sealing oil the inlet port and utilizing trapped air to start the piston gives the operator an interval of time to throw valve 17 and when port a is opened on the forward stroke of the piston the motive fluid enters at full ,volumeand pressure.

While a preferred form of the invention has been herein shown and described it is to be understood that the'invention is not limited to the specific details thereof but covers all changes, modifications, and adaptations Within the scope of the appended claim.

I claim as my invention:

A fluid pressure hammer comprising a cylinder providing a piston chamber, a piston reciprocable therein, a back head on said cylinder having a tapered cylindrical valve chamber disposed transversely of the axis of said cylinder, a closure for one end of said valve chamber having a reduced bore, a tapered valve fitting said valve chamber and disposed therein, said valve having reduced portions at its opposite ends, a handle on one reduced end to provide for manual operation of said valve, a securing member on the other reduced end of said valve to engage said closure and limit the projection of said valve within said valve chamber, resilient means interposed between said valve and said closure yieldingly to urge said valve toward the small end of said valve chamber, said back head having ports and passages for the pressure fluid, and means-substantially centrally of said valve for controlling said ports and passages comprising a deep arcuate groove in said valve always in communication with a port leading to the rear end of said piston chamber for'connecting the latter either to the pressure fluid supply or to atmosphere and a small and shallow groove at a few de- .seal against leakage of the pressure fluid.

Signed by me at Detroit, in the county of Wayne, and State of Michigan, this 15th day of June, 1928.

EDWARD W. STEVENS. 

